This invention relates generally to oil drilling and, more specifically, to measuring an amount of oil produced by a well.
Production of oil and related petrochemicals generally begins with drilling wells into the Earth""s crust to tap underground oil reserves. Drilling oil wells represents a considerable investment because the wells often must be drilled in remote locations and/or be drilled very deeply to reach oil. Moreover, the investment is a risky proposition because the drilling may not reach oil.
Considering how expensive and risky it is to drill oil wells, maintaining the wells is an important concern. If a well stops being productive, it is desirable to shut down the well rather than wastefully invest in its continued operation. Thus, it is desirable to monitor a well""s production to determine whether it continues to be a viable well. Even more importantly, it is desirable to monitor a well""s production to prevent a productive well from being lost. On occasion, a well""s production may decline sharply if the well should become blocked or otherwise impeded. If timely action is taken to address the impediment, the well can continue to be productive. On the other hand, without timely action, the well can be lost permanently, resulting in a waste of the investment to drill and maintain the well to that point.
Monitoring a well""s production to review its viability or prevent loss of the well is not a simple proposition. The output of such wells usually includes not only oil, but, also natural gas, water, and other substances. It is not desirable to invest in continued operation of an oil well that is yielding only water. More importantly, a formerly oil-producing well beginning to increasingly yield water may indicate a serious problem. If the problem is left untreated, the well could be lost.
A flow meter alone may indicate that the well is producing when, in fact, the well is producing only water. As a result, a more precise form of monitoring is desired. Unfortunately, valuable oil can exist in many different consistencies ranging from a prototypical thick, black crude to a very thin, gasoline-like fluid. Thus, successfully augmenting the flow meter to determine production of oil is not as simple as gauging the thickness of a flow of fluid being produced. An accurate assessment of the percentage of the water contained in the flow of fluid, known as a xe2x80x9cwater cut,xe2x80x9d is desired to be able to actually assess the well""s production.
To address this need, a number of different technologies have been devised to measure oil production. Unfortunately, these technologies tend to involve devices that are expensive, large, delicate, and highly sophisticated. For example, oil measuring devices using gamma rays or microwaves can monitor a flow of fluid drawn from a well and accurately gauge the amount of oil contained in that flow. Unfortunately, these devices also present a number of drawbacks, foremost of which is that these devices tend to be very expensive. As a result, it is not practical to acquire such a device for each well to continually monitor the well""s production. Typically, these devices are moved around to periodically spot-check various wells. Moving these devices around in itself is a problem because the equipment is large and heavy, and must be carried by truck from site to site. Unfortunately, by the time a well is due for spot-check and the equipment is moved on-site, a permanent problem may have arisen resulting in the well already having been lost.
Current technologies also present other concerns. Devices using radiation, to name one example, can be sensitive and require sophisticated care for routine upkeep. Moreover, radiation devices beyond a certain nominal output need to be licensed and regulated, adding to the complexity of their use. Moreover, such devices, used improperly, can present an environmental or human hazard.
To improve on these technologies, researchers have focused on ways to separate oil from foreign matter, natural gas, water, and other substances in the well. If the oil can be separated, then it can be a relatively simple matter to gauge a quantity of oil being produced. Given time, this separation is not a problem. Foreign matter can be separated from the oil by passing it through a filtering medium, comparable with the way that foreign matter is filtered from an automobile""s oil supply by passing the automobile""s oil through an oil filter. Separating the natural gas also is usually not difficult, because the less dense natural gas expands and rises out of the oil. In addition, given time, mixed oil and water also will separate themselves. Oil has a lesser density than water. Thus, if mixed oil and water are left in a collection tank, the oil will rise to the top and the water will sink to the bottom. The oil can then be collected by siphoning the oil off the top of the tank, or the water can be drained from the bottom of the tank, leaving only the oil in the tank. However, it may not be practical to allow enough time for mixed oil and water to separate themselves. Further, faster technologies to separate oil from other fluids and substances continue to prove to be complicated, difficult, and/or costly.
Thus, there is unmet need in the art for a better, cheaper, and safer way to measure an amount of oil contained in a flow of fluid extracted from an oil well.
The present invention provides an apparatus, system, and method for inexpensive and reliable measurement of an amount of oil within a flow of fluid extracted from a well. In general, capacitance of a fluid represents a good measure of a relative amount of oil contained in the flow of fluid when the flow of fluid contains approximately not less than one-half oil, although capacitance does not provide as helpful of a measure for fluids that are less than one-half oil. On the other hand, conductance of a fluid generally represents a good measure of a relative amount of oil contained in the flow of fluid when the flow of fluid contains approximately not more than one-half oil, although conductance does not provide as clear a measure for fluids that are more than one-half oil. Thus, combining measurement of capacitance and conductance provides a good measure of the relative amount of oil and water in a flow of fluid regardless of the relative percentage of each contained in the flow of fluid. Embodiments of the present invention measure capacitance and conductance of a flow of fluid at varying depths in the flow of fluid for obtaining an accurate measure of the amount of oil contained in the flow of fluid.
More particularly, embodiments of the present invention provide an apparatus, systems, and method for measuring an amount of oil in a flow of fluid at varying depths of the flow of fluid. A support structure is configured to be submerged in a flow of fluid and to support a plurality of sensors. A plurality of sensor arrays is disposed on the support structure with each of the sensor arrays being disposed at positions corresponding to varying depths of the flow of fluid and being configured to measure properties of a localized flow of fluid. Each of the sensor arrays includes a capacitance sensor including one or more capacitance sensors being configured to respond to a localized capacitance of the localized flow of fluid adjacent to the capacitance sensor with the capacitance sensor being coupled to a pair of conductors. Each of the sensor arrays also includes a conductance sensor configured to measure a localized conductance of the localized flow of fluid, the conductance sensor being configured to generate a conductance signal. The local capacitance and the conductance signal generated by each of the sensor arrays can be used to assess the relative proportions of oil and water in the flow of fluid at varying depths in the flow of fluid.
In accordance with still further aspects of the invention, the capacitance and conductance signals can be digitized and provided to a computing module configured to calculate the proportion of oil in the localized flow of fluid. The computing module is configured to use the capacitance to calculate the localized relative amount of oil in the localized flow of fluid when no less than one-half of the localized flow of fluid includes oil, and to use the conductance to calculate the localized relative amount of oil in the localized flow of fluid when approximately not more one-half of the localized flow of fluid includes oil. Additional sensors can be used to measure other fluid properties such that the computing module can adjust the amount of oil calculations to reflect these properties. A telemetry module can be configured to communicate the amount of oil to a data collection system.